tbuckley/cabot-search huggingface dataset:
CNSC-27. LOSS OF CAPICUA IMPAIRS OLIGODENDROGENESIS IN THE DEVELOPING MOUSE BRAIN
Authors: Joanna Pyczek, Courtney F Hall, Michael Johnston, Divya Singhal, Marco Gallo, Sorana Morrissy, Jennifer Chan
Journal: Neuro-Oncology (2023)

Abstract INTRODUCTION 70% of all oligodendrogliomas (ODG) harbor hemizygous loss-of-function Capicua (Cic) mutations. Cic is a transcriptional repressor downstream of MAPK signaling. Loss of Cic in neural precursors has been linked to increased proliferation and developmental bias towards differentiation-incompetent oligodendrocyte precursor cells (OPCs). This study aims to elucidate the consequences of OPC-specific Cic loss for oligodendroglia development and assess its contribution to ODG formation. METHODS Pdgfra-CreERT2;Cicfl/+;Rosa26EYFP (heterozygote control, Cic-HET) and Pdgfra-CreERT2;Cicfl/fl;Rosa26EYFP (homozygous knockout, Cic-KO) mice were used to induce Cic deletion and EYFP expression in OPCs during the postnatal wave of oligodendrocyte production (P3+P5). Double labeling with BrdU at P6 and EdU 6 hours prior to experimental endpoint was used to birthdate and assess active proliferation, respectively. Cic knockout was confirmed on the genomic level by qPCR. Formalin-fixed mouse brains were analyzed at 7-, 14- and 28-days post injection (dpi) for expression of proliferation and oligodendrocyte stage-specific markers by multiplex immunofluorescent staining. FACS-sorting was used to enrich for recombined cells based on EYFP expression. The 10x Genomics platform was used to analyze the single cell transcriptome (scRNAseq) of Cic-KO vs Cic-HET brains at designated time points. RESULTS 7dpi Cic-KO brains displayed an increased percentage of Pdgfra+ OPCs (25.76% KO vs. 15.95% HET) and a decreased percentage of CC1+ mature oligodendrocytes (27.69% KO vs. 33.93% HET) compared to heterozygote control. Cic-KO OPCs showed an increased proliferation rate as demonstrated by higher frequency of Ki67+ (3.16% HET vs 7.26%KO) and EdU+ (22.47% HET vs 44.44% KO) cells. scRNAseq revealed upregulation of genes involved in “nervous system development” and downregulation of “myelination” program upon Cic knockout. CONCLUSION We showed that OPC-specific Cic knockout results in increased cellular proliferation and maturation defects in the developing mouse brain. Cic loss may contribute to ODG formation by promoting developmental programs and inhibiting oligodendrocyte maturation in postnatal OPCs.
EPCO-30. UNCOVERING MECHANISMS OF RESISTANCE IN PEDIATRIC HIGH-GRADE GLIOMA (PHGG)
Authors: Devarshi Mukherji, Santiago Haase, Joshua Welch, Pedro Lowenstein, Maria Castro
Journal: Neuro-Oncology (2023)

Abstract Pediatric high-grade gliomas (pHGGs) are currently the leading cause of cancer-related deaths in children, remaining incurable in most cases. A molecular subgroup of pHGGs harbor G34R mutations in the histone H3.3, although the mechanisms of the H3.3-G34R/V are not well established. In most of the patients, the tumors resist radiation and relapse after standard of care (SOC). We aim to study the molecular mechanisms mediating resistance in these tumors. Knowing why certain tumors resist treatment allows us to implement targeted therapies. We performed single cell RNA sequencing on 3 non-treated (NT) glioma bearing mice, 3 mice resistant to treatment (R), and 3 mice susceptible to treatment (S). We isolated the tumor tissue (including tumor microenvironment) and processed the cells for single cell RNA sequencing. Using R, the single-cell RNA sequencing data was converted to Seurat datasets for analysis and subsequently combined and clustered using UMAP. We used the ScType and SingleR software tools to annotate cell types. After cell annotation, Gene Set Enrichment Analysis (GSEA) was performed between R and S tumors for each cell cluster as well as NT vs Treated. GSEA showed that susceptible tumor cells showed increased immune responses when compared to resistant cells. Additionally, resistant cells showed increased neuronal phenotypes as well as suppression of the ERK 1/2 cascade pathway in comparison to susceptible cells. There were also numerous differences in immune cell subpopulations, which may help uncover mechanisms of resistance. For example, certain immune cells show signs of increased epigenetic modifications in resistant vs. susceptible glioma cells. Our results indicate that the resistance of pHGG to treatment is associated with the establishment of immunosuppressive signals from tumor cells, and the suppression of tumor growth mediated by downregulation of the MAPK/ERK cascade.
MODL-37. MODELING REVERSIBLE TUMORIGENESIS IN CEREBRAL ORGANOIDS
Authors: Maya Graham, Paolo Codega, Carl Campos, Subhiksha Nandakumar, Marc Rosenblum, Cristina Antonescu, Meaghan Grogan, Jamal Benhamida, Tejus Bale, Andreas von Deimling, Nicholas Socci, Ingo Mellinghoff
Journal: Neuro-Oncology (2023)

Abstract Human cerebral organoids have emerged as a new approach to modeling the role of cancer-associated genes in tumorigenesis ex vivo. Here, we asked whether high-grade tumorigenesis in cerebral organoids is a reversible process. Using inducible cassettes carrying key oncogenic mutations histone H3K27M, dominant negative p53 and activated PDGFRA, we show that their expression in cerebral organoids reproducibly drives high grade malignant transformation in vitro and in vivo, including in orthotopic xenografts. We characterize this transformation as a fusion-negative rhabdomyosarcoma (FN-RMS) phenotype and identify a putative FN-RMS cell-of-origin in cerebral organoids. Finally, we show this transformation is dependent on persistent transgenic oncogene expression, as oncogene withdrawal causes complete tumor regression. These findings demonstrate that cerebral organoids may be used to pinpoint previously unappreciated and distinct roles of different mutations in tumor development and maintenance.
EXTH-73. IN VIVO EFFECTS OF EPCAM-DIRECTED CAR T CELLS IN COMBINATION WITH PD-1 CHECKPOINT BLOCKADE IN LUNG CANCER BRAIN METASTASIS
Authors: Jens Blobner, Laura Dengler, Constantin Eberle, Julika J Herold, Tao Xu, Nico Teske, Philipp Karschnia, Hellen Ishikawa-Ankerhold, Marion Subklewe, Niklas Thon, Joerg-Christian Tonn, Veit Buchholz, Louisa von Baumgarten
Journal: Neuro-Oncology (2023)

Abstract BACKGROUND Metastatic lung cancer is incurable once it spreads to the brain. Chimeric antigen receptor (CAR) T cells show promise in hematologic malignancies but face challenges in solid tumors, particularly in brain tumors, due to a highly immunosuppressive tumor microenvironment (TME), tumor antigen (TA) heterogeneity and impeded infiltration and persistence at the tumor site. To test the efficacy of CAR T cells and to find strategies for potentially enhancing its efficacy, CAR T cells were applied with and without checkpoint-blockade to treat lung cancer brain metastasis. METHODS We used an immunocompetent syngeneic orthotopic cerebral metastasis model combined with a chronic cranial window and repetitive intracerebral two-photon laser scanning microscopy (TPLSM). This allowed us to observe fluorescent tumor cells and CAR T cells in vivo at a single cell level over time. We injected red fluorescent EpCAM-transduced Lewis Lung carcinoma cells (EpCAM-LL/2tdT) into the brain tissue, followed by injection of EpCAM-directed or mock CAR T cells. Animals received anti-PD-1 and the respective isotype control via intraperitoneal injections. RESULTS EpCAM-directed CAR T cells were generated and showed substantial anti-tumor effects in vitro. Local injection into EpCAM-LL/2 tumor-bearing mice led to intratumoral accumulation of CAR T cells, resulting in reduced tumor growth compared to undirected CAR T cells translating into long-term survival in a fraction of animals. However, intratumoral CAR T cell numbers decrease over time pointing towards insufficient persistence. Interestingly, anti-PD-1 treatment did not enhance intratumoral CAR T accumulation, persistence and anti-tumor efficacy. CONCLUSION Our findings demonstrate the great potential of cell-based treatment approaches for the treatment of lung cancer brain metastases and underlines the necessity of further investigations to enhance infiltration and persistence in solid tumors.
IMMU-25. ANALYSIS OF IMMUNOSUPPRESSIVE MYELOID CELLS IN THE GLIOBLASTOMA TUMOR MICROENVIRONMENT REVEALS THERAPEUTICALLY TARGETABLE IMMUNOMODULATORY SIGNALS ACROSS POPULATIONS
Authors: Mohammad Asad, Julio Inocencio, Celina Crisman, Benjamin Himes
Journal: Neuro-Oncology (2023)

Abstract Immunosuppression in glioblastoma (GBM) remains a critical and poorly understood barrier to the development of effective novel therapies. Increasing evidence points to the critical role of immunosuppressive myeloid cells in the immunosuppressive tumor microenvironment and an intriguing target for ameliorating tumor-mediated immune suppression. Efforts to characterize the myeloid milieu in the tumor microenvironment have revealed a highly heterogenous population of cells with the capacity to exert immunosuppressive effects. In order to maximize the efficacy of potential therapeutic targets, we sought to identify immune checkpoint markers expressed across a range of immunomodulatory myeloid cell populations in the tumor microenvironment of patients undergoing resection for GBM. Freshly collected ultrasonic aspirate obtained during the primary surgery for GBM resection (based on preoperative imaging and intraoperative frozen section, later confirmed on final pathology) was prepared for high dimensional flow cytometry to quantify the immune checkpoint marker expression profile of a number of described immunosuppressive myeloid cell populations, including both monocytic and granulocytic myeloid-derived suppressor cells (mMDSC and gMDSC), and CD16+ non-classical monocytes (NCM). mMDSCs expressed particularly high levels of TIGIT (53.9±19.27%), which was also highly expressed in the NCM population (25.03±5.44%). NCMs also demonstrated high levels of B7H3 expression (39.85±18.05%), which has recently been implicated as an important immune checkpoint protein in GBM. gMDSCs demonstrated a rather different expression profile, with significantly higher levels of VISTA expression than other immunomodulatory markers (p&amp;lt; 0.05). These findings underscore the diversity of immunomodulatory signaling in the tumor-associated myeloid cell compartment, emphasizing the challenges in developing single-target immune checkpoint inhibitor therapy in GBM. Nevertheless, this data points to some common patterns of expression across major immunomodulatory cell populations that remain understudied in GBM and could herald more promising avenues of immunotherapy development.
RBIO-06. COMBINING FLASH RADIOTHERAPY WITH GD2-CAR T CELL IMMUNOTHERAPY IN DIFFUSE INTRINSIC PONTINE GLIOMA
Authors: Haille Soderholm, Zara Kiger, Wonju Kim, Robbie Majzner, Bonnie Lau
Journal: Neuro-Oncology (2023)

Abstract Diffuse Intrinsic Pontine Glioma (DIPG) is the leading cause of brain tumor related deaths in pediatric cancers. DIPG is completely lethal, and palliative radiation therapy (RT) to control symptoms is currently the standard-of-care treatment for DIPG, therefore effective treatment is urgently needed. In recent phase 1 clinical trials, the promising potential for using chimeric antigen receptor T cell immunotherapy against the disialoganglioside GD2 (GD2-CART) has been established, where 75% of patients exhibited clinical and radiographic improvement. There has also been emerging evidence advocating for the combined use of GD2-CART therapy with conventional radiation (CONV-RT) to enhance the immune response in other solid brain tumors. Ultra-high dose rate radiotherapy, abbreviated as FLASH-RT, is an emerging radiation technique shown to reduce normal brain tissue damage while preserving tumor control, as compared to CONV-RT. It is currently unknown how FLASH-RT will affect CART therapy. We hypothesize that effective treatment for DIPG can be achieved by combining FLASH-RT with GD2-CART immunotherapy. We have shown FLASH-RT to equivocally kill DIPG cells as well as the standard-of-care, CONV-RT; Given the neurological tissue sparing effects of FLASH-RT, this radiotherapy alone could be an improvement for DIPG treatment. Additionally, we have validated that GD2 is highly expressed in our DIPG cell line, suggesting high GD2-CART target specificity. Additionally, we have found that GD2 expression on DIPG tumor cells remains unchanged upon treatment with FLASH-RT. Therefore, we can utilize FLASH-RT to target GD2 CART while sparing normal tissue and minimizing neurotoxicity, allowing for a promising avenue of combination treatment for this devastating pediatric cancer.
NIMG-53. IMAGING FEATURES AND CONSIDERATION OF PROGRESSION PATTERN OF DIFFUSE HEMISPHERIC GLIOMAS, H3 G34-MUTANT
Authors: Yuji Kibe, Fumiharu Ohka, Kazuya Motomura, Kosuke Aoki, Sachi Maeda, Junya Yamaguchi, Hiroki Shimizu, Ryuta Saito
Journal: Neuro-Oncology (2023)

Abstract BACKGROUND Diffuse hemispheric gliomas, H3 G34-mutant (DHGs-G34m) are newly recognized pediatric-type diffuse high-grade gliomas. We describe detail imaging features of seven cases of DHGs-G34m and consider about progression pattern of DHGs-G34m. RESULTS H3 G34R or H3 G34V was detected by sanger sequencing in all tumors. Mean age of onset was 16.5 years (range: 10-26). Tumors were located on frontal (2), parietal (2), temporal lobe (1) and insular cortex (1), respectively. In one case, gliomatosis cerebri-like multiple lesions involving the cortex and basal ganglia occurred. Magnetic resonance imaging showed T2/FLAIR high lesions with poor contrast enhancement in all cases. All tumors harbored restriction of diffusion. Cystic component and hemorrhage were observed in five and three cases, respectively. Six patients underwent preoperative positron emission tomography. Strong accumulation of methionine and partial accumulation of FDG in all cases. All tumors harbored T2/FLAIR high lesions in the deep white matter, most of which showed methionine accumulation. All patients underwent surgery (total resection in one case, partial resection in five cases, and biopsy in one case) followed by radiation chemotherapy. The mean progression free survival was 9.9 months (range: 1.6-33.1 months). All tumors harbored diffuse infiltration along the white matter, which was temporarily reduced by bevacizumab, but eventually invaded into cerebral peduncle via pyramidal tract and into contralateral brain via corpus callosum or anterior commissure in six cases. Extensive infiltration of tumor cells into the contralateral brain and brain stem was confirmed histopathologically in the autopsy brain of one case. The mean overall survival was 21.6 months (range: 8.9-48.3 months). CONCLUSION DHGs-G34m showed deep white matter infiltration from the time of initial onset, which made gross total resection difficult. Residual lesions extensively infiltrated along the white matter and eventually invaded the brainstem and contralateral brain, leading to death.
EXTH-52. LONG-ACTING RECOMBINANT INTERLEUKIN-7, NT-I7, IMPROVES SURVIVAL FOLLOWING ONCOLYTIC ZIKA VIRUS TREATMENT IN THE SB28 IMMUNOSUPPRESSIVE AND TREATMENT-RESISTANT MURINE GLIOMA MODEL
Authors: Yuping Li, Tong Hu, Ashwani Kesarwani, Amanda De Andrade Costa, Ritvik Illindala, Alexandra Wolfarth, Sara Ferrando-Martinez, Se Hwan Yang, Byung Ha Lee, Michael S Diamond, Milan Chheda
Journal: Neuro-Oncology (2023)

Abstract Glioblastoma (GBM) does not respond to immunotherapy for several reasons, including limited cancer-specific neoantigens and poor T-cell infiltration. The SB28 murine glioma model recapitulates these aspects of human GBM. Zika virus (ZIKV) treatment of GL261 and CT2A-bearing mice resulted in significant survival improvement through multiple mechanisms, including direct tumor killing and induction of a local CD8+ T-cell anti-tumor response, but ZIKV is less effective against SB28 tumors. Previously, we published that a long-acting human IL-7, rhIL-7-hyFc (NT-I7, efineptakin alfa; NeoImmuneTech Inc.), increases T-cell abundance and improves tumor infiltration. Therefore, we hypothesize that combining NT-I7 with oncolytic ZIKV therapy will enhance the anti-tumor response and improve survival in mice bearing SB28 syngeneic tumors. 1×103 SB28 tumor cells were intracranially implanted in C57BL/6J mice. Mice were treated with NT-I7 on post tumor implantation day 7 and 10, followed by intratumoral ZIKV on day 14. Tumor burden was assessed using bioluminescence imaging; mice were monitored for survival and bled weekly to assess the systemic T-cell response to NT-I7. Subcutaneous injection of NT-I7 significantly boosted systemic T-cell abundance compared to control (5,623 cells/uL vs. 136 cells/uL, p &amp;lt; 0.05), particularly cytotoxic CD8+ T-cells (4,776 cells/uL vs. 47 cells/uL, p &amp;lt; 0.05). This increased abundance of CD8+ T-cells peaked at 7 days after initial treatment and persisted for 21 days. NT-I7 monotherapy did not confer any survival benefit. However, the combination of NT-I7 and ZIKV treatment resulted in significant improvement in survival compared to NT-I7 or ZIKV treatment alone (p &amp;lt; 0.05). Treatment with NT-I7 primes the immune system by expanding the circulating CD8+ T-cell population by 100-fold. Timing the oncolytic ZIKV injection with the peak in peripheral CD8+ T-cells greatly improved survival in the immunotherapy resistant SB28 glioma model. These data suggest a role for NT-I7 as an adjunct to various T-cell mediated treatment strategies for GBM.
RADT-47. MARGIN REDUCTION WITH THE INTRODUCTION OF INTRA-FRACTIONAL MONITORING USING IDENTIFY SGRT FOR FRAMELESS STEREOTACTIC CRANIAL RADIOSURGERY (SRS)
Authors: Tai Tran, Lee Anderson, Yunfei Hu, Cecelia Gzelle
Journal: Neuro-Oncology (2023)

Abstract The purpose of this study was to evaluate the potential for margin reduction in clinical treatment settings based on the accuracy of Varian Identify SGRT (Surface-Guided Radiation Therapy). The study considered various factors such as patient setup variations, intrafraction movement, and unique facial features. Identify version 2.3.1 was installed on a Truebeam v2.7 system and commissioned according to AAPM TG3021 test recommendations. Identify generated reports on patient offsets in all six degrees of freedom during motion monitoring. These offsets were retrospectively compared with radiographic images (CBCT and MV planar images) to determine the accuracy of patient positioning achieved using surface guidance. A retrospective analysis of 36 patients was performed for a total of 125 fractions. The characteristics of the patient cohort (age range from 39 – 92 years) consisted of a mixture of 8 benign, 28 malignant lesions, 11 single, 25 standard fully-fractionated treatments and anatomical sites such as parietal, frontal, ventricle, base of skull, pons and acoustic neuromas. RESULTS: show that for this clinical cohort, the variance between Identify and radiographic imaging ranges from -0.02 to 0.08 cm, -0.09 to 0.10 cm, -0.09 to 0.09 cm and -0.81 to 0.74 degrees for the vertical, longitudinal, lateral and rotation respectively. This average variance in the translational axes is 0.0cm ± 0.0014 cm, indicating no directional preference. The 3D vector of the displacement detected achievable by Identify is 1 mm within a 95% confidence interval (CI). Based on the findings, the researchers concluded that a minimum GTV-PTV (Gross Tumor Volume-Planning Target Volume) margin of 1 mm is appropriate for intrafraction monitoring with Identify SGRT on the TrueBeam system for stereotactic cranial treatments. This information can increase the radiation oncologist's confidence in patient positioning during treatment delivery and potentially lead to a decrease in the GTV-PTV margin.
NCOG-40. PATTERNS OF PROGRESSION IN PATIENTS WITH NEWLY DIAGNOSED PRIMARY CENTRAL NERVOUS SYSTEM LYMPHOMA FOLLOWING TREATMENT WITH HIGH-DOSE METHOTREXATE
Authors: Louis Cappelli, Jennifer Newman, Muhammad Sharif, Allison Kayne, Narendranath Epperla, Ahmed Elguindy, Joshua Palmer, Iyad Alnahhas, Wenyin Shi
Journal: Neuro-Oncology (2023)

Abstract INTRODUCTION Primary central nervous system lymphoma (PCNSL) is a rare form of non-Hodgkin's lymphoma that primarily affects the brain. Recurrence of PCNSL within the central nervous system is common, but patterns of intracranial recurrence following induction chemotherapy have not been extensively studied. This study aims to elucidate the patterns of recurrence and progression in PCNSL. METHODS Adult patients from two institutions with newly diagnosed PCNSL that received HD-MTX based chemotherapy from 2011-2023 were included. Patient charts and diagnostic imaging were retrospectively reviewed. The pattern of recurrence/progression was reviewed by comparing the initial diagnostic MRI to the first recurrence MRI (T1 post-contrast and FLAIR sequence). Distant recurrences were defined as separate lesions from the previous primary enhancing lesion, located outside the initial FLAIR abnormality observed on imaging. Local recurrences were characterized as new lesions overlapping with the primary enhancing lesion/FLAIR abnormality. RESULTS 25 patients were identified to have been diagnosed with PCNSL and progressed through initial definitive treatment with HD-MTX based chemotherapy. 2/25 received initial management with radiation therapy. Median age at diagnosis was 66 years. The median time to progression was 18.1 months (Range; 0.9-70). Twelve of the 25 patients had a complete response to initial systemic therapy, 6 had a partial response, and 7 patients had disease progression through chemotherapy. Eleven of the 25 patients were found to have multifocal disease at diagnosis. 13/25 (52%) patients had distant recurrence only, 5/25(20%) had only local recurrence, and 7/25 (28%) displayed both local and distant recurrence pattern. CONCLUSION In this retrospective review, for patients diagnosed with PCNSL who are able to undergo HD-MTX we identified that the majority of disease recurrence is outside or distant to the primary disease site vs locally (80% vs 20%). Such findings should be verified with a larger cohort and can help direct further consolidation strategies.